title: Modulation of ethylene biosynthesis by ACC and AIB reveals a structural and functional relationship between the K15NO3 uptake rate and root absorbing surfaces.
abstract: The modification of root traits in relation to nitrate uptake represents a source for improvement of nitrogen uptake efficiency. Because ethylene signalling modulates growth of exploratory and root hair systems more rapidly (minutes to hours) than nitrate signalling (days to weeks), a pharmacological approach was used to decipher the relationships between root elongation and N uptake. Rape seedlings were grown on agar plates supplied with 1mM K(15)NO3 and treated with different concentrations of either the ethylene precursor, ACC (0.1, 1, and 10 μM) or an inhibitor of ethylene biosynthesis, AIB (0.5 and 1 μM). The results showed that rapid modulation of root elongation (up to 8-fold) is more dependent on the ethylene than the nitrate signal. Indeed, ACC treatment induced a partial compensatory increase in (15)N uptake associated with overexpression of the BnNRT2.1 and BnNRT1.1 genes. Likewise, daily root elongation between treatments was not associated with daily nitrate uptake but was correlated with N status. This suggested that a part of the daily root response was modulated by cross talks between ethylene signalling and N and C metabolisms. This was confirmed by the reduction in C allocation to the roots induced by ACC treatment and the correlations of changes in the root length and shoot surface area with the aspartate content. The observed effects of ethylene signalling in the root elongation and NRT gene expression are discussed in the context of the putative role of NRT2.1 and NRT1.1 transporters as nitrate sensors.
authors.affiliation: Université de Caen Basse-Normandie, UMR EVA, F-14032 Caen cedex, France.
authors.forename: Lucile
authors.initials: L
authors.lastname: Lemaire
authors.forename: Carole
authors.initials: C
authors.lastname: Deleu
authors.forename: Erwan
authors.initials: E
authors.lastname: Le Deunff
mesh_terms: D000598:Amino Acids, Cyclic / Q000494:pharmacology*; D000621:Aminoisobutyric Acids / Q000494:pharmacology*; D027321:Anion Transport Proteins / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D029688:Brassica napus / Q000737:chemistry / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism*; D005030:Ethylenes / Q000096:biosynthesis*; D018506:Gene Expression Regulation, Plant; D007700:Kinetics; D000091285:Nitrate Transporters; D009566:Nitrates / Q000737:chemistry / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000737:chemistry / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D017680:Potassium Compounds / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000598:Amino Acids, Cyclic; D000621:Aminoisobutyric Acids; D027321:Anion Transport Proteins; D005030:Ethylenes; D000091285:Nitrate Transporters; D009566:Nitrates; D010940:Plant Proteins; D017680:Potassium Compounds; C023863:1-aminocyclopropane-1-carboxylic acid; C036216:ethylene; C023844:potassium nitrate
keywords: Brassica napus; ethylene signalling; hydrogen cyanide; nitrate sensing; nitrate transporters NRT2.1 and NRT1.1; nitrate uptake; nutrient use efficiency; root elongation.